4-6-/2-62 ATTORNEYS. George L. Malloy. June 23, 1970 G. L. MALOY ETAL 3,516,514. Edword L. Dold. Filed Feb. 4, 1969

Transcription

1 June 23, 1970 G. L. MALY ETAL 3,16,14 SAFETY CNTRL FR AERIAL BUCKET. TRUCK Filed Feb. 4, 1969 BY INVENTRS. George L. Malloy Edword L. Dold 4-6-/2-62 ATTRNEYS.

2 United States Patent ffice 3,16,14 Patented June 23, ,16,14 SAFETY CNTRL FR AERAL BUCKET. TRUCK George L. Malloy, Bethel Road, R.D. 2, Lansdale, Pa , and Edward L. Dold, 39 Eisenhower Ave., Woodlyn, Pa Filed Feb. 4, 1969, Ser. No. 796,379 Int, C. B66f II/04 U.S. C Claims ABSTRACT F THE DISCLSURE In a hydraulically-operated aerial bucket truck, of the type used by electric utility companies for working on overhead lines and poles, a manually operable safety control is disclosed to allow the lineman, from his ele wated position in the aerial bucket, to shut down the hydraulic system by utilizing the pneumatic pressure avail able in the bucket for driving his pneumatic tools. BACKGRUND F THE INVENTIN Electric utilities conventionally use an aerial bucket truck for work on poles and overhead wires. Because the bucket and the articulated boom which carries the bucket are necessarily moved to positions close to the electric wires which may be operating at high voltages, it is necessary from a safety point of view that at least the upper leg of the boom be not made of metal or other conducting material nor carry electric wiring in order to avoid any possibility of establishing a dangerous con nection between the high voltage wires and ground. Thus, in the conventional aerial bucket truck, at least the upper leg of the articulated boom is made of insulating plastic, as for example, high strength glass filament reinforced epxy. The insulated boom bucket truck is ordinarily supplied with two drive systems, one a drive system for driving the boom which carries the bucket, which conventionally may be a hydraulic system, and the other a pneumatic system for driving the pneumatic tools used by the line al It is conventional to provide two sets of controls for the hydraulic system. ne set of controls is usually located on the mast at the base of the boom in the truck body. The other set of hydraulic controls is located at the bucket itself. Thus, the boom may be moved and posi tioned by the lineman in the bucket. r the boom may be manipulated by a workman down in the truck body. In the conventional system, the hydraulic controls on the mast at the base of the boom are over-riding controls, which is to say, these lower controls, when operated, will over-ride the hydraulic controls in the bucket. In the conventional aerial bucket truck, if the hydraulic controls in the bucket become fouled by tree branches, or if other mishap should occur, resulting in hazardous movement of the boom and bucket, the lineman in the bucket can de-activate the bucket hydraulic controls and immobilize the boom by operating a lever to place a hy draulic shunt across the bucket hydraulic controls. When he does so, the lower hydraulic controls on the mast at the base of the boom in the truck body remain opera tive, and the boom can be manipulated by the man in the truck to bring the bucket down safely. If, however, in the conventional truck just described, a tree or tree branch should fall across the over-riding hydraulic controls on the mast down at the base of the boom, and if, as a result thereof, the bucket and boom are caused to move out of control, the lineman in the aerial bucket has no means for stopping the boom move ment. This is, of course, a very dangerous and undesirable situation SUMMARY F THE INVENTIN In accordance with the present invention, a manually operable safety control is provided in the otherwise con ventional hydraulically-operated bucket truck whereby the lineman in the bucket may depressurize and thus de activate the hydraulic system. In accordance with the invention, an air-operated or pneumatic switch is mounted on the truck body and con nected to insulating pneumatic lines extending up through the insulating articulated boom to the aerial bucket. In the presence of pneumatic pressure, the air-operated switch closes its contacts to complete an electrical cir cuit which includes a solenoid operated valve. This valve is made to control a bypass hydraulic shunt across the hydraulic pump. In normal operation, pneumatic pres sure is applied to the air-operated switch to energize the solenoid operated valve to hold the pump bypass closed, thereby blocking flow of hydraulic fluid through the shunt path across the hydraulic pump. If, however, the over riding hydraulic controls on the mast at the base of the boom become disabled, as by a tree branch falling there across, or the like, hazardous movement of the bucket may result, which the lineman cannot control because the bucket controls have been over-ridden. In Such emergency, the lineman in the aerial bucket can stop the otherwise uncontrolled movement of the boom, by manually throw ing a safety lever to reduce, as by venting, the pneumatic pressure in the insulating hoses extending down through the boom to the pneumatic switch on the truck body. This reduction in air pressure opens the air-operated switch, which in turn opens the electrical circuit through the solenoid operated valve, moving the valve from shut to open position. This establishes a hydraulic shunt path across the hydraulic pump and reduces the hydraulic pressure in the rest of the hydraulic system effectively to zero, thereby de-activating the hydraulic drive and stopping movement of the boom. An advantageous feature is that the pump is still running and the hydraulic system can be instantly re-activated by the lineman in the bucket or by the truck operator. As a further feature of the invention, when the pneumatic switch is released, as just described, to de-activate the hydraulic drive, the throttle of the truck motor is automatically moved in a direcion to slow down the motor, thereby avoiding racing of the motor which would otherwise occur when the hydraulic pump load was removed. BRIEF DESCRIPTIN F THE DRAWING FIG. 1 is a perspective view of a typical aerial bucket truck; FIG. 2 is an enlarged view of the aerial bucket show ing the controls at the bucket; FIG. 3 is an enlarged view showing the controls on the mast which supports the articulated boom; FIG. 4 is a schematic illustration of the pneumatic means, the electrical circuit, and the hydraulic means, provided in accordance with the present invention to al low the lineman in the aerial bucket to de-activate the hydraulic drive to stop movement of the boom. DESCRIPTIN F THE PREFERRED EMBDIMENT FIG. 1 illustrates a typical aerial bucket truck 10 hav ing in the truck body a mast 12 which supports an articu lated boom comprising a lower boom 21 and an upper boom 22. The upper boom 22 is made of high strength in sulating material, such as glass filament reinforced epoxy, and carries at its upper end a lineman's bucket. FIG. 2 is an enlarged view of the bucket which carries the lineman. The bucket may also be made of high strength insulating material, or for bare-hand operation

3 3 at high voltage it may be metal lined or of metal to pro vide a Faraday cage or electrostatic screen. As shown in FIG. 2, attached to the bucket is a hydraulic control box 31 having three control levers. The hydraulic control box 31 and the 'connections thereto are conventional, and accordingly the connections have been omitted from the drawing, but it is to be mentioned that the hydraulic lines or conduits which extend down through the boom to connect the control box 31 to the hydraulic system in the truck body are made of insulating material such as plastic. Also extending through the insulated boom are insulating air hoses or conduits, not shown, and in ac cordance with the present invention, an insulating hose 41 which is a tap from the compressed air supply. A compressed-air outlet connection 44 to the air supply line 41, for driving pneumatic tools, is disposed on the upper boom 22 adjacent the bucket and within reach of the lineman, In accordance with the invention, compressed air is supplied through tap hose 41 to an adjustable reducing valve 46, and then is supplied, at reduced pressure, to a lever-operated emergency valve 4, and then, by way of an insulating hose 42 is fed back down through the boom arms 22 and 21 to the pneumatic switch 0 mounted on the truck body. FIG. 3 is an enlarged fragmentary view of the mast 12 in the truck body and shows that the mast 12 carries the over-riding hydraulic control box 1 mounted on the mast below the pivotal connection of the lower boom 21 to the mast. The over-riding hydraulic control box 1 in FIG. 3 is indicated as having three control levers, but the connections to the control box are conventional and are not shown in the drawing. FIG. 4 illustrates schematically the means provided by the present invention to provide an additional safety control to the lineman working in the aerial bucket. In FIG. 4, the insulated bucket, shown in dotted lines, is shown as having installed thereat the reducing valve 46 and the manually operable pneumatic safety valve 4. Manual control of the valve 4 is afforded by a lever 47 which may be moved by the lineman from the solid line position to the dotted-line position identified as 47. 'When the lever 47 is in its normal solid-line position, the two-way air valve 4 connects line 43 to hose 42, and compressed air, reduced in pressure by the reducing valve 46, is supplied by way of insulating hose 42 down through the insulating boom to the air-operated or pneumatic switch 0 mounted on the body of the truck 10. : When compressed air from the compressed air supply is applied at reduced pressure to the normally-open switch 0, as during normal operation, the switch 0 is held in the contact-closing position, and current from the truck battery 1 flows through the winding 3 of a nor mally-open solenoid valve 4 to maintain the valve 4 closed. Thus, pump pumps oil from line 61 (which is connected to an oil reservoir) out through the line 62, and the hydraulic pressure in line 62 is carried to the over-riding hydraulic control box 1 in the truck body and then up through insulating lines in the articulated boom to the bucket hydraulic control box 31 to pro vide control at both places for the movement of the boom. As previously indicated, in the conventional truck, and also in the truck of the present invention, the hydraulic control box 1 mounted on the mast 12 in the truck body has over-riding control relative to the hydraulic control box 31 in the bucket. Thus, so long as the control box 1, is operable, a workman in the truck has over-riding control over the movement and positioning of the boom, and, so long as the over-riding controls in the truck body are operative, they may be used by a workman stationed below to protect the lineman in the bucket in the event the hydraulic controls 31 in the bucket (which in normal operation the lineman uses to move himself around) be come damaged. 3,16, If, however, as previously indicated, the over-riding hydraulic controls 1 in the truck should malfunction or be damaged, as by tree or tree branches falling there across, neither the workman in the truck nor the line man in the bucket has thereafter any control over the hydraulic pressure drive and the boom and bucket may be driven toward and into a high tension line, or other dangerous situation, before a workman in the truck can rush into the truck cab to shut off the truck motor. Fur thermore, should the truck motor be shut down to de activate the hydraulic system and stop the movement of the bucket, the lineman, who may perhaps be injured and/or unconscious, could be in a precarious position from which it would be desirable that he be extracted with all possible dispatch. This would generally require restarting the truck motor, which could introduce an ap preciable delay. The dangerous condition just postulated is remedied by the present invention for, in the emergency situation just described wherein the hydraulic controls 1 in the truck are damaged and can no longer control the hy draulic system, the lineman in the aerial bucket can merely throw the lever 47 from the solid line position to the dotted line position indicated in FIG. 4. This dis connects the input pressure line 43 from the hose 42, and connects the hose 42 to the atmospheric vent line 48. Thus, the air pressure in hose 42 is very rapidly re duced and the pneumatic switch 0 releases, opening the electrical circuit, and de-energizing the winding 3 of the solenoid valve 4. Valve 4 opens and the hydraulic pressure in line 62 immediately drops to zero, or substan tially zero, since pump now only drives the oil through the bypass lines 64 and 6. With no hydraulic pressure in the hydraulic line 62, the boom immediately stops moving and thus the danger that the uncontrolled boom and bucket would have moved into a high tension line or other dangerous position, is avoided. The use of a pneumatic switch 0 which can be held closed by a reduced value of pneumatic pressure allows the hydraulic drive to the boom to be de-activated in a minimum of time, for when the lineman throws the lever 47 to the vent position 47, the pressure in hose 42 is very quickly reduced to a value equal to the release value of the air-operated switch 0. To assure maximum speed of opening of the pneumatic switch 0, the reducing valve 46 is adjusted for an operative pressure in the hose 42 slightly above the minimum necessary to hold the Switch 0 in contact-closing position. The lineman may immediately restore the operative condition of the pneumatic controls, as for example when the emergency is over, by restoring the lever 47 from the dotted line vent position 47 to the Solid line operating position. This action pressurizes the pneumatic switch 0 which energizes the solenoid valve 4 to close the pump bypass and restore pressure in the hydraulic system. To allow the workman in the truck to re-activate the hydraulic pressure system after the lineman in the bucket has thrown the safety lever to the vent position, a spring loaded push-button switch 70 is provided for the electrical circuit to short out the contacts of the air-operated Switch. 0. Such push-button switch 70 may conveniently be mounted on the mast 12 in the truck body. The push-button switch 70 is preferably spring-loaded to open position. After, or during an emergency, the truck operator may re-activate the hydraulic system regardless of the position of the emergency valve 4 by holding the switch 70 closed with one hand and he can then operate the adjacent over-riding hydraulic controls 1 with his free hand, regardless of the positioning or condition of the bucket controls. - It is apparent from the description that the present invention provides, in an aerial bucket truck, an elec trically safe pneumatic-electro-hydraulic system with provides the lineman with an additional measure of safety and which is itself fail-safe so far as loss of air pressure

4 or loss of electric power is concerned. For, in the case of loss of air pressure and/or electric power, the hydrau lic pressure is removed from the boom drive and the boom and bucket remain motionless until the defect is remedied. As previously indicated, when the air-operated switch 0 is released to open-circuit position, and the electrical circuit is thereby opened, a relay may be operated to move the throttle of the truck motor to a slow-down posi tion to avoid racing of the truck motor when the hy draulic load is removed. Such an arrangement is shown in FIG. 4 of the application. In FIG. 4, the throttle 80, which controls the speed of the motor of truck 10, is biased toward idling or slow-speed position by a biasing spring 81. In normal operation, the air-operated Switch 0 holds its contacts closed, thereby closing the circuit through the battery 1. It will be seen that when the con tacts of the air-operated switch 0 are closed, current flows not only through the winding of the solenoid valve 3 but also through the winding of a normally-open throttle-control relay 82, thereby closing the contacts of relay 82 and causing current to also flow through the coil of a plunger solenoid 83 whose plunger is connected by a flexible link 8 to the throttle 80 causing the solenoid plunger to pull the flexible link 8 toward the right, as viewed in FIG. 4, thereby holding the throttle 80 away from the idling position and causing the truck motor to run at the proper operative speed. The plunger-solenoid 83 may be of any suitable conventional type such as the series L. solenoids marketed by Synchro-Start Products, Inc. of Skokie, Ill. When, at the time of an emergency, the lineman in the aerial bucket throws the lever 47 to the dotted line position 47, and air is vented from the air hose 42 as previously described, and the contacts of the air-operated valve 0 open, the circuit through the wind ing of the throttle relay 82 is opened and current flow therethrough is interrupted. The contacts of throttle relay 82 open and the flow of current through the winding of the solenoid 83 ceases. The plunger of the solenoid is thereupon pulled to the left by the action of the spring 81, and the throttle 80 moves to idling position. What is claimed is: i. In an aerial bucket truck having a truck body; an insulating boom supported by said truck body; an insu lating aerial bucket carried at the upper end of said boom; a hydraulic pressure system for driving said boom, said hydraulic pressure system including a pump, first hydrau lic controls at said bucket for moving said boom; second hydraulic controls at said truck body for moving said boom in overriding relation to said first controls; and insulating hydraulic lines interconnecting said first and Second controls; a pneumatic pressure system for supply ing pneumatic pressure to the bucket for operating a lineman's tools, said pneumatic system including a source of compressed air and an insulating hose connecting sys tem; the improvement which is characterized by the pro vision of: (a) a hydraulic bypass at said truck body shunting said pump, (b) said bypass including a solenoid valve which is open when said solenoid is not energized; (c) an electrical circuit including a power supply, at said truck body for energizing said solenoid valve to close said valve, thereby to shut off said bypass; (d) an air-operated switch at said truck body, said Switch being coupled to said pneumatic pressure sys tem and having contacts in said electrical circuit which are closed when air pressure is applied to said Switch: (e) a manually-operable two-position pneumatic safety valve at said aerial bucket and connected to said pneumatic pressure system and by insulating hose to said air- operated switch for controlling the supply of air pressure to said air-operated switch at said truck body; (f) said safety valve in one position allowing air pres 3,16, sure from said pneumatic system to be supplied to said air-operated switch to hold the contacts of said switch in electrical-contact-closing position, said safety valve in the other position reducing the air pressure to said air-operated switch to release said switch to electrical-contact-opening position, where by the lineman in said aerial bucket by operating the safety valve to said other position may open the electrical circuit to de-energize the solenoid valve to establish the bypass shunting said pump, thereby to remove the hydraulic pressure from the boom drive. 2. Apparatus according to claim 1 characterized in (a) a manually-operable switch is connected in said electric circuit across the contacts of said air-operated Switch for closing said electric circuit when said air operated Switch is in circuit-opening position; (b) said manually-operable switch is disposed at said truck body in proximity to said second hydraulic controls for enabling a workman stationed at said truck body to operate said manually-operable switch simultaneously with said second hydraulic controls; (c) whereby, while said safety valve is in said other position said workman may close said electrical cir cuit to close the bypass shunting the pump by operat ing said manually-operable switch, thus restoring hy draulic pressure to the boom drive and enabling him to operate said second hydraulic controls for causing desired movement of the boom. 3. Apparatus according to claim 1 characterized in (a) said pump is driven by the truck motor; (b) spring means are provided biasing the truck motor (c) said electrical circuit includes a throttle control relay and a throttle solenoid connected to the throttle of the truck motor, said throttle control relay being energized when said safety valve is in said one posi tion, thereby to close an electrical circuit to energize said throttle solenoid to overcome the biasing action of said spring means and to hold said throttle at faster than idling speed, said throttle control relay being deenergized when said safety valve is in said other position, thereby to open the circuit to de energize said throttle solenoid and allow said biasing spring means to return the throttle to idling-speed position. 4. In an aerial bucket truck having a truck body; an insulating boom supported by said truck body; an insu lating aerial bucket carried at the upper end of said boom; a hydraulic pressure system for driving said boom, said hydraulic pressure system including a pump driven by the truck motor, first hydraulic controls at said bucket, Second over-riding hydraulic controls at said truck body and insulating lines interconnecting said first and second controls; a pneumatic pressure system for supplying pneu matic pressure to the bucket for operating the lineman's tools, Said pneumatic system including a source of com pressed air and an insulating hose connecting system; the improvement which is characterized by the provision of: (a) a hydraulic bypass at said truck body shunting said pump; (b) said bypass including a solenoid valve; (c) an electrical circuit, including a power supply, at said truck body for controlling said bypass solenoid valve to close said valve during normal operation, thereby to shut off said bypass; (d) an air-operated switch at said truck body, said Switch being coupled to said pneumatic pressure sys tem and having contacts in said electrical circuit which are closed or open according to the condition of said air-operated switch; (e) a manually-operable two-position safety valve at said aerial bucket and connected through said pneu matic pressure system to said air-operated switch

5 7 for controlling the condition of said air-operated Switch; (f) whereby the workman in said aerial bucket by operating the safety valve to one of its positions may actuate said air-operated Switch in said truck body thereby to actuate the solenoid valve, thereby to establish a bypass to shunt said pump, thereby to remove the hydraulic pressure from the boom drive,. Apparatus according to claim 4 characterized in (a) a manually-operable spring-return switch is con nected in said electric circuit across the contacts of said air-operated switch for closing said electric cir cuit when said air-operated switch is in circuit-open ing position; (b) said spring-return switch is disposed at said truck body in proximity to said second hydraulic controls for enabling a workman stationed at said truck body to operate said spring-return switch simultaneously with said second hydraulic controls; (c) whereby, while said safety valve is in its position for conditioning said air-operated switch to the con tact-opening condition, said workman may close said electrical circuit by operating said spring-return switch. 6. Apparatus according to claim 4 characterized in (a) spring means are provided biasing the truck motor (b) said electrical circuit includes a throttle control relay and a throttle solenoid connected to the throttle of the truck motor, said throttle control re lay being energized when said safety valve is in said one of its positions, thereby to close a second elec trical circuit to energize said throttle solenoid to overcome the biasing action of said spring means and to hold said throttle at faster than idling speed, said throttle control relay being de-energized when said safety valve is in its other position, thereby to open said second electrical circuit to de-energize said throttle solenoid, thereby to allow said biasing spring means to return the throttle to idling-speed position. 7. In an aerial bucket truck having a truck body; a boom Supported by said truck body; an aerial bucket carried by said boom; a hydraulic pressure system for driving said boom; said hydraulic pressure system includ ing boom-positioning controls and a pump driven by the truck motor; a pneumatic pressure system for supplying pneumatic pressure at said bucket; the improvement which is characterized by the provision of: (a) a hydraulic bypass shunting said pump; 3,16,14 ls (b) electromechanical bypass control means in said... bypass for, closing said bypass upon being energized and for opening said bypass when de-energized; (c) an electric circuit including a source of electri... city for energizing said bypass control means; (d) pnuematic switch means in said circuit for clos ing: said circuit when pressurized and opening said circuit, when depressurized;..... (e) a manually-operable two-position pneumatic safe ty valve in said bucket adapted to connect said pneumatic switch means to said pneumatic pressure system or to an atmospheric vent, said safety valve in one position causing said pneumatic switch means to be pressurized and in the other position to be de pressurized;.. (f) whereby in said one position of said safety valve said bypass is closed to render said boom-position ing controls operative and in said other position of said Safety valve said bypass is open and said boom positioning controls are inoperative and said boom is immobilized. 8. Apparatus according to claim 7 characterized in (a) spring means are provided biasing the truck motor (b) said electric circuit includes a throttle control relay and a throttle solenoid connected to said throttle; (c) said throttle control relay being energized when said safety valve is in said one position, thereby to close a second electric circuit for energizing said - - throttle solenoid to overcome the biasing action of said spring means and to hold said throttle at faster than-idling-speed position; (d) said throttle relay being de-energized when said safety valve is in said other position, thereby open ing said second electric circuit to de-energize said throttle solenoid and allow said spring means to return the throttle to idling-speed position. References Cited UNITED STATES PATENTS 3,127,92 4/1964 Baerg ,132,718 /1964 Pierce et al ,379,279 4/1968 Slusher ,467,217 9/1969 Zwight REINALDP. MACHAD, Primary Examiner 182-2, 148 U.S. C. X.R.